Retroreflective structures of the type utilized herein are described in detail in the Jungersen U.S. Pat. No. 2,380,447, issued Jul. 31, 1945, the Hoopman U.S. Pat. No. 4,588,258, issued May 13, 1986 and the Stamm U.S. Pat. No. 3,712,706, issued Jan. 23, 1973 (each of which is incorporated herein in its entirety by reference.) In particular FIG. 15 of the Jungersen patent illustrates in plan view a sheet of reflective prisms which reflect light at an angle other than perpendicular to the reflector. The Hoopman patent discloses cube-corner retroreflective articles in which the optical axis of the elements in an array of prism element pairs are tilted toward one edge of the elements, when considered from the front surface of the article on which light to be retroreflected images. This tilt direction is herein defined as "positive" type tilt; as contrasted to the tilt direction shown in FIG. 15 of the Jungersen patent in which the optical axis of prism pairs tilts away from the common edge.
Walter, U.S. Pat. No. 5,171,624 discloses microprism reflective sheeting in which prism pairs are tilted with respect to one another at an angle of 3.degree.-10.degree., a prism size of 0.006-0.025 (space between apices) and wherein at least one prism side surface is arcuate.
Benson U.S. Pat. No. 5,122,902 discloses retroreflective cube-corner elements with separation surfaces between elements and truncated cube-corner elements.